The use of illuminating devices is well-known in the medical industry to provide personnel with adequate lighting during medical procedures such as examinations and surgery. Typically, illuminating devices are attached to a ceiling or wall mount or alternatively to a floor stand and are adapted to be placed into a desired position to satisfy the lighting needs of medical personnel. An illuminating device employing prisms to concentrate light onto an operating area or field is described in U.S. Pat. No. 3,941,993 which is incorporated herein in its entirety by reference. Commercial embodiments of such a prismatic light which has a cupola mounted, for example, on a ceiling suspension is available from ALM EQUIPEMENTS Hospitaliers of France, having a distributor, ALM Surgical Equipment Inc. of Santa Ana, Calif., as illustrated and described in a technical manual entitled "Operating Theatre Light ECL 701" (1983) which is also incorporated herein in its entirety by reference.
Generally, the device of the '993 patent includes in a preferred embodiment a prism assembly formed of a plurality of prisms 13 which are positioned generally as shown in FIG. 3 thereof with respect to one or more light sources 14, 15 or 16. The light emitted by the source or sources is directed by a corresponding number of toroidal optical systems 17, 18 and 19 onto the prisms 13. Preferably the individual prisms are straight and grouped into sectors as shown in FIG. 4 of the '993 patent. In addition, the prisms are oriented so that light from the source(s) is directed by the toroidal optical system(s) perpendicularly onto the faces of the prisms, is totally reflected by the opposite face and then is refracted by the exit face. The apex angles of the prisms allows for directing the light rays onto the desired portions of the field 21 as shown in FIG. 5 on the '993 patent. In this manner, the device of the '993 patent illuminates the operating field of a patient lying on an operating table with substantially uniform illumination, excellent shadow control and good depth of field.
Another prismatic surgical light employing curved prisms is set forth in French Patent 1,495,007 which is also incorporated herein in its entirety. This French patent is generally described in column 1 of the '993 patent and illustrated schematically in FIG. 1 thereof. Unlike the device of the '993 patent, the device of the aforementioned French patent did not generally provide for uniform illumination as illustrated in FIG. 2 of the '993 patent. The curved prim of the French Patent '007 was a completely circular lens that was not broken into sectors as proposed by the '993 patent.
Despite the advantages of the device according to the '993 patent, there remains a continuing need to improve the convenience and performance of the lighting device for medical use. I have invented an improved medical illuminating device which provides additional improvements to presently available medical prismatic lights. These improvements address the needs of various medical personnel in circumstances where various illumination patterns may be desired. For example, the present invention provides that once the light is positioned within a wide range of positions, then tilting of the exit faces of the prisms allows for variation of the intensity of illumination or for change of the area of illumination. In addition, such tilting capability with a prismatic lighting system allows for relocation of the optimization of the depth of field while still allowing for generally uniform illumination. Also, the present invention provides for lower or greater intensity throughout the region of illumination.